Backport of EE changes: Allow Labels::FindOrCreateService to find ancestor group labels

backport of EE changes in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/5954

What does this MR do?

1. Allow Labels::FindOrCreateService to find ancestor group labels
2. Add authorize for viewing project board.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

backport of EE changes as it is a common need to reference labels from ancestor groups.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)